Correct KMeans scoring function doc

[najeeb-kazmi]

Fixes #4011

[codecov]

Codecov Report

Merging #4705 into master will decrease coverage by 0.01%.
The diff coverage is 98.26%.

@@            Coverage Diff             @@
##           master    #4705      +/-   ##
==========================================
- Coverage   75.85%   75.84%   -0.02%     
==========================================
  Files         951      951              
  Lines      172435   172594     +159     
  Branches    18617    18632      +15     
==========================================
+ Hits       130796   130898     +102     
- Misses      36464    36517      +53     
- Partials     5175     5179       +4

Flag	Coverage Δ
#Debug	75.84% <98.26%> (-0.02%)	⬇️
#production	71.45% <95.83%> (+0.01%)	⬆️
#test	90.49% <99.2%> (-0.14%)	⬇️

Impacted Files	Coverage Δ
...Microsoft.ML.Tests/Transformers/NormalizerTests.cs	100% <ø> (ø)	⬆️
...est/Microsoft.ML.Predictor.Tests/TestPredictors.cs	67.94% <ø> (ø)	⬆️
src/Microsoft.ML.Data/Evaluators/EvaluatorBase.cs	54.25% <ø> (ø)	⬆️
test/Microsoft.ML.TimeSeries.Tests/TimeSeries.cs	87.85% <ø> (ø)	⬆️
...crosoft.ML.TimeSeries.Tests/TimeSeriesDirectApi.cs	99.27% <ø> (ø)	⬆️
src/Microsoft.ML.Data/Training/TrainerUtils.cs	66.26% <ø> (ø)	⬆️
src/Microsoft.ML.Data/Data/RowCursorUtils.cs	74.58% <ø> (ø)	⬆️
...est/Microsoft.ML.Tests/FeatureContributionTests.cs	98.55% <ø> (ø)	⬆️
...ML.Tests/Scenarios/IrisPlantClassificationTests.cs	100% <ø> (ø)	⬆️
...ests/TrainerEstimators/MatrixFactorizationTests.cs	97.84% <ø> (ø)	⬆️
... and 36 more